阅读说明：本技术 一种阻燃聚酰亚胺泡沫材料及其制备方法、应用 (Flame-retardant polyimide foam material and preparation method and application thereof ) 是由 周光远 聂赫然 顾铭茜 黄志成 于 2021-08-06 设计创作，主要内容包括：本发明提供了一种阻燃聚酰亚胺泡沫材料,所述阻燃聚酰亚胺泡沫材料中含有粉煤灰微胶囊；所述阻燃聚酰亚胺泡沫材料具有多孔结构；所述粉煤灰微胶囊复合在所述聚酰亚胺泡沫中。该阻燃聚酰亚胺泡沫材料中含有微胶囊粉煤灰,而且进一步的将粉煤灰以特定的形式被两种囊材包裹,形成具有特定结构的阻燃聚酰亚胺泡沫材料。本发明提供的阻燃聚酰亚胺泡沫材料,将粉煤灰微胶囊与聚酰亚胺泡沫复合,又特别控制微胶囊粉煤灰的加入量,在保证聚酰亚胺泡沫力学性能和绝热性能不受影响的同时,利用粉煤灰自身的阻燃特性、以及囊材的协同阻燃作用,使聚酰亚胺泡沫兼具更加优异的阻燃性能；而且制备工艺简单、易于控制,有利于实现工业化规模生产和应用。(The invention provides a flame-retardant polyimide foam material, which contains fly ash microcapsules; the flame-retardant polyimide foam material has a porous structure; the fly ash microcapsule is compounded in the polyimide foam. The flame-retardant polyimide foam material contains microcapsule fly ash, and the fly ash is further wrapped by two capsule materials in a specific form to form the flame-retardant polyimide foam material with a specific structure. According to the flame-retardant polyimide foam material provided by the invention, the fly ash microcapsule and the polyimide foam are compounded, and the addition amount of the microcapsule fly ash is particularly controlled, so that the polyimide foam has more excellent flame-retardant property by utilizing the flame-retardant property of the fly ash and the synergistic flame-retardant effect of the capsule material while the mechanical property and the heat insulation property of the polyimide foam are not influenced; and the preparation process is simple and easy to control, and is favorable for realizing industrial scale production and application.)

1. The flame-retardant polyimide foam material is characterized in that the flame-retardant polyimide foam material contains fly ash microcapsules;

the flame-retardant polyimide foam material has a porous structure;

the fly ash microcapsule is compounded in the polyimide foam.

2. The flame-retardant polyimide foam material as claimed in claim 1, wherein the microencapsulated fly ash comprises a fly ash capsule core and a double-layer capsule wall coated on the outer layer of the fly ash capsule core;

the double-layer capsule wall comprises an aluminum hydroxide capsule wall and a melamine-formaldehyde resin capsule wall;

the aluminum hydroxide capsule wall is an inner capsule wall;

the melamine-formaldehyde resin is an outer capsule wall.

3. The flame-retardant polyimide foam material as claimed in claim 2, wherein the particle size of the fly ash microcapsules is 50-480 μm;

the thickness of the inner layer capsule wall is 2-50 mu m;

the thickness of the outer capsule wall is 10-80 μm;

the mass ratio of the fly ash to the aluminum hydroxide is 1: (0.2 to 0.6);

the mass ratio of the fly ash to the melamine-formaldehyde resin is 1: (3.6-7.2).

4. The flame retardant polyimide foam material of claim 1, wherein the flame retardant polyimide foam material has an open cell content of 70% to 95%;

the density of the flame-retardant polyimide foam material is 6-15 kg/m³；

The fly ash microcapsules are filled in the gaps among the foam holes, are positioned in the foam holes and are attached to the hole walls of the foam holes;

the mass content of the fly ash microcapsules in the flame-retardant polyimide foam material is 3-15%;

the aperture of the flame-retardant polyimide foam material is 300-600 microns.

5. The flame-retardant polyimide foam material is characterized by comprising the following raw materials in percentage by mass:

6. the flame retardant polyimide foam of claim 5, wherein said isocyanate comprises one or more of 8122, PM-200, PM-400, NE-466, 8214, and PM-8223;

the content of isocyanate in the isocyanate is 25-38%;

the aromatic dianhydride comprises one or more of BTDA, PMDA and DSDA;

the solvent comprises one or more of DMF, DMSO, and DMAC;

the catalyst comprises an amine catalyst and/or a metal catalyst;

the blowing agent comprises one or more of methanol, ethanol, acetone, water and 2-butoxyethanol;

the foam stabilizer comprises one or more of water-soluble silicone oil, silicone oil and polyether modified silicone oil.

7. A method for preparing the flame retardant polyimide foam material as defined in any one of claims 1 to 4 or the flame retardant polyimide foam material as defined in any one of claims 5 to 6, comprising the steps of:

1) mixing aromatic dianhydride and a solvent to obtain a first solution;

mixing the fly ash microcapsule, water, a foaming agent, a foam stabilizer and a catalyst again to obtain a second solution;

2) premixing the first solution and the second solution obtained in the above steps, mixing with isocyanate, foaming and molding in a mold, and curing to obtain the flame-retardant polyimide foam material.

8. The method according to claim 7, wherein the mixing means includes heating and stirring;

the mixing temperature is 50-85 ℃;

the rotating speed of the mixing is 200-550 r/min;

the mixing time is 3-12 h;

the catalyst comprises one or more of stannous octoate, dibutyltin dilaurate, N, N-dimethyl cyclohexylamine, bismuth isooctanoate, N, N ' -diethyl piperazine and N, N, N ', N ' -tetramethyl alkylene diamine;

the means of remixing may include ultrasonic mixing and/or mechanical agitation.

9. The method of claim 7, wherein the final mixing comprises high speed mixing;

the rotating speed of the final mixing is 2000-6000 r/min;

the final mixing time is 10-30 s;

the foaming and forming time is 15-40 min;

the curing temperature is 200-280 ℃;

the curing time is 3-10 h.

10. The flame-retardant polyimide foam material as defined in any one of claims 1 to 4, the flame-retardant polyimide foam material as defined in any one of claims 5 to 6, or the flame-retardant polyimide foam material prepared by the preparation method as defined in any one of claims 7 to 9, is applied to the fields of new energy automobiles, rail transit, and ships.

Technical Field

The invention belongs to the technical field of polyimide foam materials, and particularly relates to a flame-retardant polyimide foam material as well as a preparation method and application thereof.

Background

The polyimide foam material is a light porous material, and has the properties of light weight, excellent high and low temperature resistance, heat insulation, sound absorption, noise reduction, flame retardance, insulation and the like. The high-performance polyimide foam can resist 250-300 ℃ for a long time and 400-500 ℃ for a short time, and is one of the materials with the best heat stability in organic polymers. The high-performance flame-retardant polyimide foam material also has the advantages of extremely low temperature resistance, no brittle fracture in liquid helium at the temperature of 269 ℃ below zero and the like. The polyimide foam material has been widely paid attention to in various social circles by virtue of excellent performances in the aspects of high and low temperature resistance, flame retardance, fire resistance, sound absorption, noise reduction, oxidation resistance, hydrolysis resistance and the like, so that the rapid development of the polyimide foam material industry is promoted. Polyimide foams have been reported to be used in their naval vessel systems for marine protection in over 15 countries as thermal insulation. In addition, polyimide foam is also a good choice for wave-transparent materials, structural materials and seat materials in aerospace vehicles.

With the development of electronics, electricians, telecommunications and construction industries, the flame retardant requirements for polymer materials in the industry are becoming higher and higher. The flame retardant used in the polymer material enhances the flame resistance of the polymer material, and meanwhile, the flame retardant is foreign 'impurities' to the structural integrity of the polymer material and has certain incompatibility with the polymer material, so that the physical and mechanical properties of the polymer material are influenced to a greater or lesser extent.

Therefore, it is very important how to find a more suitable way to improve the flame retardant property of the polyimide foam material, and solve the above problems of the flame retardant, so as to meet the increasingly stringent flame retardant requirements of various fields.

Disclosure of Invention

In view of this, the technical problem to be solved by the present invention is to provide a flame retardant polyimide foam material, and a preparation method and an application thereof. According to the novel flame-retardant polyimide foam material provided by the invention, the microcapsule fly ash is compounded with the polyimide foam, so that the polyimide foam has more excellent flame-retardant property while the mechanical property and the heat insulation property of the polyimide foam are not influenced; and the preparation process is simple and easy to control, and is favorable for realizing industrial scale production and application.

The invention provides a flame-retardant polyimide foam material, which contains fly ash microcapsules;

the flame-retardant polyimide foam material has a porous structure;

the fly ash microcapsule is compounded in the polyimide foam.

Preferably, the microencapsulated fly ash comprises a fly ash capsule core and a double-layer capsule wall coated on the outer layer of the fly ash capsule core;

the double-layer capsule wall comprises an aluminum hydroxide capsule wall and a melamine-formaldehyde resin capsule wall;

the aluminum hydroxide capsule wall is an inner capsule wall;

the melamine-formaldehyde resin is an outer capsule wall.

Preferably, the particle size of the fly ash microcapsule is 50-480 μm;

the thickness of the inner layer capsule wall is 2-50 mu m;

the thickness of the outer capsule wall is 10-80 μm;

the mass ratio of the fly ash to the aluminum hydroxide is 1: (0.2 to 0.6);

the mass ratio of the fly ash to the melamine-formaldehyde resin is 1: (3.6-7.2).

Preferably, the opening ratio of the flame-retardant polyimide foam material is 70-95%;

the density of the flame-retardant polyimide foam material is 6-15 kg/m³；

The fly ash microcapsules are filled in the gaps among the foam holes, are positioned in the foam holes and are attached to the hole walls of the foam holes;

the mass content of the fly ash microcapsules in the flame-retardant polyimide foam material is 3-15%;

the aperture of the flame-retardant polyimide foam material is 300-600 microns.

The invention provides a flame-retardant polyimide foam material which comprises the following raw materials in parts by mass:

preferably, the isocyanate comprises one or more of 8122, PM-200, PM-400, NE-466, 8214 and PM-8223;

the content of isocyanate in the isocyanate is 25-38%;

the aromatic dianhydride comprises one or more of BTDA, PMDA and DSDA;

the solvent comprises one or more of DMF, DMSO, and DMAC;

the catalyst comprises an amine catalyst and/or a metal catalyst;

the blowing agent comprises one or more of methanol, ethanol, acetone, water and 2-butoxyethanol;

the foam stabilizer comprises one or more of water-soluble silicone oil, silicone oil and polyether modified silicone oil.

The invention provides a flame-retardant polyimide foam material as defined in any one of the above technical schemes or a preparation method of the flame-retardant polyimide foam material as defined in any one of the above technical schemes, which comprises the following steps:

1) mixing aromatic dianhydride and a solvent to obtain a first solution;

mixing the fly ash microcapsule, water, a foaming agent, a foam stabilizer and a catalyst again to obtain a second solution;

2) premixing the first solution and the second solution obtained in the above steps, mixing with isocyanate, foaming and molding in a mold, and curing to obtain the flame-retardant polyimide foam material.

Preferably, the mixing mode comprises heating and stirring;

the mixing temperature is 50-85 ℃;

the rotating speed of the mixing is 200-550 r/min;

the mixing time is 3-12 h;

the catalyst comprises one or more of stannous octoate, dibutyltin dilaurate, N, N-dimethyl cyclohexylamine, bismuth isooctanoate, N, N ' -diethyl piperazine and N, N, N ', N ' -tetramethyl alkylene diamine;

the means of remixing may include ultrasonic mixing and/or mechanical agitation.

Preferably, the final mixing mode comprises high-speed stirring and mixing;

the rotating speed of the final mixing is 2000-6000 r/min;

the final mixing time is 10-30 s;

the foaming and forming time is 15-40 min;

the curing temperature is 200-280 ℃;

the curing time is 3-10 h.

The invention also provides the application of the flame-retardant polyimide foam material in any one of the technical schemes, the flame-retardant polyimide foam material in any one of the technical schemes or the flame-retardant polyimide foam material prepared by the preparation method in any one of the technical schemes in the fields of new energy automobiles, rail transit and ships.

The invention provides a flame-retardant polyimide foam material, which contains fly ash microcapsules; the flame-retardant polyimide foam material has a porous structure; the fly ash microcapsule is compounded in the polyimide foam. Compared with the prior art, the invention aims at the problem that the physical and mechanical properties of the high polymer material are influenced by adopting various flame retardants in the conventional flame-retardant polyimide foam material. The invention particularly selects the microcapsule technology, and the compatibility of the flame retardant and the polymer material can be improved by utilizing the microcapsule, thereby reducing or eliminating the adverse effect of the flame retardant on the physical and mechanical properties of the polymer product; the release amount of toxic components in the flame retardant in the processing process of the polymer material is reduced, and the environment pollution is avoided; meanwhile, the active components are protected from the influence of environmental conditions such as weather and the like and the damage of the outside, so that the storage period is prolonged. Therefore, it is very important to introduce the microcapsule technology into the polyimide foam material to improve the flame retardant property of the polyimide foam material so as to meet the increasingly stringent flame retardant requirements of various fields.

The invention particularly designs a novel flame-retardant polyimide foam material which contains microcapsule fly ash, and the fly ash is further wrapped by two capsule materials in a specific form to form the flame-retardant polyimide foam material with a specific structure. The polyimide foam material provided by the invention contains the fly ash microcapsules, the fly ash has good flame retardant property, the aluminum hydroxide capsule material on the surface is decomposed by heating, a large amount of latent heat of evaporation is absorbed, the temperature of a combustion system is reduced, the flame retardant effect is realized, a large amount of water vapor is generated, the smoke generation rate and the smoke generation amount of a high polymer during combustion are reduced, the flame retardant and smoke suppression effect is realized, and the aluminum hydroxide is used for coating the fly ash, so that the synergistic flame retardant effect is expected to be realized in an application system. The melamine-formaldehyde capsule material (also called melamine resin) on the surface is a resin which is fine and crosslinked, very hard and good in thermal stability, and has higher mechanical strength, good heat resistance, water resistance, flame resistance, excellent electrical property and self-extinguishing property. The flame retardant has high flame retardant efficiency, has good compatibility with high polymers, can perform decomposition reaction at high temperature, absorb a large amount of heat, release ammonia, influence the melting behavior of materials and accelerate the carbonization of the materials into coke, and has simple preparation process and low cost.

According to the flame-retardant polyimide foam material provided by the invention, the fly ash microcapsule and the polyimide foam are compounded, and the addition amount of the microcapsule fly ash is particularly controlled, so that the polyimide foam has more excellent flame-retardant property by utilizing the flame-retardant property of the fly ash and the synergistic flame-retardant effect of the capsule material while the mechanical property and the heat insulation property of the polyimide foam are not influenced; and the preparation process is simple and easy to control, and is favorable for realizing industrial scale production and application.

Experimental results show that the density of the flame-retardant polyimide foam material prepared by the invention is 9.7kg/m³The compression strength is 15.3kPa, the thermal conductivity coefficient is 0.041W/(m.K), the oxygen index is 45 percent, the comprehensive performance is excellent, and the flame retardant property is outstanding.

Detailed Description

For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.

All of the starting materials of the present invention, without particular limitation as to their source, may be purchased commercially or prepared according to conventional methods well known to those skilled in the art.

All of the starting materials of the present invention are not particularly limited in their purity, and the present invention preferably employs purity requirements that are conventional in the art of analytical grade or polyimide foam preparation.

All the raw materials, the marks and the acronyms thereof belong to the conventional marks and acronyms in the field, each mark and acronym is clear and definite in the field of related application, and the raw materials can be purchased from the market or prepared by a conventional method by the technical staff in the field according to the marks, the acronyms and the corresponding application.

The invention provides a flame-retardant polyimide foam material, which contains fly ash microcapsules;

the flame-retardant polyimide foam material has a porous structure;

the fly ash microcapsule is compounded in the polyimide foam.

In the invention, the microencapsulated fly ash preferably comprises a fly ash capsule core and a double-layer capsule wall coated on the outer layer of the fly ash capsule core.

In the present invention, the double-layered capsule wall preferably comprises an aluminum hydroxide capsule wall and a melamine-formaldehyde resin capsule wall.

In the present invention, the aluminum hydroxide capsule wall is preferably an inner capsule wall.

In the present invention, the melamine-formaldehyde resin is preferably an outer capsule wall.

In the invention, the particle size of the fly ash microcapsule is preferably 50-480 μm, more preferably 100-430 μm, more preferably 150-380 μm, more preferably 200-330 μm, more preferably 250-280 μm.

In the invention, the thickness of the inner capsule wall is preferably 2-50 μm, more preferably 12-40 μm, and more preferably 22-30 μm.

In the invention, the thickness of the outer capsule wall is preferably 10-80 μm, more preferably 20-70 μm, more preferably 30-60 μm, and more preferably 40-50 μm.

In the present invention, the mass ratio of the fly ash to the aluminum hydroxide is preferably 1: (0.2 to 0.6), more preferably 1: (0.25 to 0.55), more preferably 1: (0.3 to 0.5), more preferably 1: (0.35-0.45).

In the present invention, the mass ratio of the fly ash to the melamine-formaldehyde resin is preferably 1: (3.6 to 7.2), more preferably 1: (4.1 to 6.7), more preferably 1: (4.6-6.2), more preferably 1: (5.1-5.7).

In the present invention, the open cell ratio of the flame retardant polyimide foam material is preferably 70% to 95%, more preferably 75% to 90%, and still more preferably 80% to 85%.

In the invention, the density of the flame-retardant polyimide foam material is preferably 6-15 kg/m³More preferably 8 to 13kg/m³More preferably 10 to 11kg/m³。

In the present invention, the fly ash microcapsules are preferably filled in one or more of the cell gaps, in the cells, and attached to the cell walls of the cells, and more preferably filled in the cell gaps, in the cells, or attached to the cell walls of the cells.

In the invention, the mass content of the fly ash microcapsules in the flame-retardant polyimide foam material is preferably 3% to 15%, more preferably 5% to 13%, and more preferably 7% to 11%.

In the invention, the pore diameter of the flame-retardant polyimide foam material is preferably 300-600 μm, more preferably 350-550 μm, and more preferably 400-500 μm.

The invention also provides a flame-retardant polyimide foam material, which comprises the following raw materials in percentage by mass:

in the present invention, the isocyanate is preferably added in an amount of 17 to 68 parts by weight, more preferably 27 to 58 parts by weight, and still more preferably 37 to 48 parts by weight.

In the present invention, the isocyanate preferably comprises one or more of 8122, PM-200, PM-400, NE-466, 8214 and PM-8223, more preferably 8122, PM-200, PM-400, NE-466, 8214 or PM-8223.

In the present invention, the isocyanate content of the isocyanate is preferably 25% to 38%, more preferably 27% to 36%, more preferably 29% to 34%, and more preferably 31% to 32%.

In the present invention, the aromatic dianhydride is preferably added in an amount of 15 to 65 parts by weight, more preferably 25 to 55 parts by weight, and even more preferably 35 to 45 parts by weight.

In the present invention, the aromatic dianhydride preferably includes one or more of BTDA, PMDA and DSDA, more preferably BTDA, PMDA or DSDA.

In the present invention, the solvent is preferably added in an amount of 13 to 41 parts by weight, more preferably 18 to 36 parts by weight, and still more preferably 23 to 31 parts by weight.

In the present invention, the solvent preferably includes one or more of DMF, DMSO, and DMAC, more preferably DMF, DMSO, or DMAC.

In the present invention, the amount of the blowing agent added is preferably 1 to 27 parts by weight, more preferably 6 to 22 parts by weight, and still more preferably 11 to 17 parts by weight.

In the present invention, the blowing agent preferably includes one or more of methanol, ethanol, acetone, water and 2-butoxyethanol, more preferably methanol, ethanol, acetone, water or 2-butoxyethanol.

In the present invention, the amount of the foam stabilizer added is preferably 2 to 19 parts by weight, more preferably 6 to 15 parts by weight, and still more preferably 10 to 11 parts by weight.

In the present invention, the foam stabilizer preferably includes one or more of water-soluble silicone oil, silicone oil, and polyether-modified silicone oil, and more preferably water-soluble silicone oil, or polyether-modified silicone oil.

In the present invention, the amount of the catalyst added is preferably 0.1 to 8.5 parts by weight, more preferably 2 to 6.5 parts by weight, and still more preferably 4 to 4.5 parts by weight.

In the present invention, the catalyst preferably includes an amine catalyst and/or a metal catalyst, more preferably an amine catalyst or a metal catalyst.

In the present invention, the water is preferably added in an amount of 25 to 49 parts by weight, more preferably 30 to 44 parts by weight, and still more preferably 35 to 39 parts by weight.

In the invention, the addition amount of the fly ash microcapsule is preferably 3-20 parts by weight, more preferably 7-16 parts by weight, and more preferably 11-12 parts by weight.

The invention is a complete and refined integral process, better ensures the structure and the characteristics of the fly ash microcapsule, better improves the flame retardance of the polyimide foam material, and simultaneously ensures the original performance of the polyimide foam material, and the preparation method of the fly ash microcapsule preferably comprises the following steps:

(a) heating and mixing the fly ash, the aluminum sulfate, the water and the dispersant solution, adding a pH regulator, keeping the temperature and stirring, and performing post-treatment to obtain powder A;

heating and mixing the melamine and the formaldehyde again, adding the pH regulator again, and standing to obtain a transparent solution in which the melamine is completely dissolved, namely a melamine-formaldehyde resin prepolymer solution;

(b) and stirring and mixing the dispersing agent, the powder A and water, adding the melamine-formaldehyde resin prepolymer solution, continuously mixing, adjusting the pH value, heating, keeping the temperature, and adjusting the pH value again to finally obtain the microencapsulated fly ash coated by the melamine-formaldehyde resin.

More specifically, the preparation method of the fly ash microcapsule can comprise the following steps:

(1) putting fly ash, aluminum sulfate and water into a three-neck flask containing a dispersant solution, stirring and dispersing, and heating to a specified temperature.

(2) Na is added dropwise₂CO₃Adjusting pH value of the aqueous solution, stirring for a certain time under heat preservation, and purifying to obtain powder A for later use.

(3) Putting melamine and formaldehyde into a three-neck flask, heating in water bath, adding a sodium carbonate solution to adjust the pH value, standing for a period of time, and completely dissolving the melamine to obtain a transparent solution, namely a melamine-formaldehyde resin prepolymer solution.

(4) The dispersant, powder A and water were added to a three-necked flask and stirred thoroughly.

(5) Adding the melamine-formaldehyde resin prepolymer solution, stirring and dispersing in a water bath, and cooling to room temperature.

(6) Adjusting pH with HAc, heating in water bath, slowly heating, stirring while maintaining the temperature, cooling, adding Na₂CO₃Adjusting the pH value of the solution. Purifying to obtain the microencapsulated fly ash coated by the melamine-formaldehyde resin.

Wherein, the mass ratio of the fly ash to the aluminum sulfate is preferably 1: (1-3), more preferably 1: (1.5-2.5).

The mass ratio of the fly ash to the water is preferably 1: (5-8), more preferably 1: (6-7).

The dispersing agent comprises one or more of sodium dodecyl sulfate, sodium hexametaphosphate and OP-10, and more preferably sodium dodecyl sulfate, sodium hexametaphosphate or OP-10.

The mass amount of the dispersant in the (a) is preferably 0.5 to 1.5%, more preferably 0.8 to 1.2%.

The stirring speed of the heating and mixing in the step (a) is preferably 100-600 r/min, more preferably 200-500 r/min, and more preferably 300-400 r/min.

The temperature of heating and mixing in the step (a) is preferably 60-90 ℃, and more preferably 70-80 ℃.

The pH regulator preferably comprises Na₂CO₃And (3) solution. In particular, the Na₂CO₃The mass concentration of the solution is preferably 10% to 30%, more preferably 15% to 25%.

The pH value after the pH regulator is added in the step (a) is preferably 4-7, and more preferably 5-6.

The time for heat preservation and stirring in the step (a) is preferably 1-6 h, more preferably 2-5 h, and more preferably 3-4 h.

The molar ratio of melamine to methanol in (a) is preferably 1: (2.5 to 3.5), more preferably 1: (2.7-3.2).

The mode of reheating and mixing in (a) comprises water bath heating. Specifically, the reheating and mixing temperature is preferably 70-90 ℃, and more preferably 75-85 ℃.

The pH value after the pH regulator is added again in the step (a) is preferably 7-9, and more preferably 7.5-8.5.

The standing time in the step (a) is preferably 0.5-3 h, more preferably 1-2.5 h, and more preferably 1.5-2 h.

The mass amount of the dispersant in (b) is preferably 1.5 to 3.5%, more preferably 2 to 3%.

The mass ratio of the powder A to the water in the (b) is preferably 1: (5-8), more preferably 1: (6-7).

The stirring speed of stirring and mixing in the step (b) is preferably 500-1000 r/min, more preferably 600-900 r/min, and more preferably 700-800 r/min.

The mass ratio of the powder A to the prepolymer solution in the step (b) is preferably 1: (3-6), more preferably 1: (4-5).

The temperature of the continuous mixing in the step (b) is preferably 60-70 ℃, and more preferably 62-68 ℃.

The pH adjusting agent in (b) preferably comprises HAc. Specifically, the pH value after the pH value is adjusted is preferably 3-6, and more preferably 4-5.

The temperature of the heat preservation in the step (b) is preferably 60-80 ℃, and more preferably 65-75 ℃.

In the step (b), the pH value is adjusted againThe reagent preferably comprises Na₂CO₃And (3) solution. Specifically, the pH value after the pH value is adjusted again is preferably 8 to 9, and more preferably 7 to 8.

The invention also provides the flame-retardant polyimide foam material in any one of the technical schemes or a preparation method of the flame-retardant polyimide foam material in any one of the technical schemes, which comprises the following steps:

1) mixing aromatic dianhydride and a solvent to obtain a first solution;

mixing the microcapsule fly ash, water, a foaming agent, a foam stabilizer and a catalyst again to obtain a second solution;

2) premixing the first solution and the second solution obtained in the above steps, mixing with isocyanate, foaming and molding in a mold, and curing to obtain the flame-retardant polyimide foam material.

Firstly, mixing aromatic dianhydride and a solvent to obtain a first solution;

and mixing the microcapsule fly ash, water, the foaming agent, the foam stabilizer and the catalyst again to obtain a second solution.

In the present invention, the mixing preferably includes heating and stirring.

In the invention, the mixing temperature is preferably 50-85 ℃, more preferably 55-80 ℃, more preferably 60-75 ℃ and more preferably 65-70 ℃.

In the invention, the rotation speed of the mixing is preferably 200-550 r/min, more preferably 250-500 r/min, more preferably 300-450 r/min, and more preferably 350-400 r/min.

In the invention, the mixing time is preferably 3-12 h, more preferably 5-10 h, and more preferably 7-8 h.

In the present invention, the catalyst preferably includes one or more of stannous octoate, dibutyltin dilaurate, N-dimethylcyclohexylamine, bismuth isooctanoate, N '-diethylpiperazine, and N, N' -tetramethylalkylenediamine, and more preferably stannous octoate, dibutyltin dilaurate, N-dimethylcyclohexylamine, bismuth isooctanoate, N '-diethylpiperazine, or N, N' -tetramethylalkylenediamine.

In the present invention, the means of remixing preferably includes ultrasonic mixing and/or mechanical stirring, more preferably ultrasonic mixing or mechanical stirring.

The flame-retardant polyimide foam material is prepared by premixing the first solution and the second solution obtained in the step, mixing the premixed solution with isocyanate, performing foaming molding in a mold, and curing.

In the present invention, the means of the final mixing preferably comprises high-speed stirring mixing.

In the invention, the rotation speed of the final mixing is preferably 2000-6000 r/min, more preferably 2500-5500 r/min, more preferably 3000-5000 r/min, and more preferably 3500-4500 r/min.

In the present invention, the time for the final mixing is preferably 10 to 30 seconds, more preferably 14 to 26 seconds, and still more preferably 18 to 22 seconds.

In the invention, the foaming time is preferably 15-40 min, more preferably 20-35 min, and more preferably 25-30 min.

In the invention, the curing temperature is preferably 200-280 ℃, more preferably 210-270 ℃, more preferably 220-260 ℃, and more preferably 230-250 ℃.

In the invention, the curing time is preferably 3-10 h, more preferably 4-9 h, and more preferably 5-8 h.

The invention also provides the application of the flame-retardant polyimide foam material in any one of the technical schemes, the flame-retardant polyimide foam material in any one of the technical schemes or the flame-retardant polyimide foam material prepared by the preparation method in any one of the technical schemes in the fields of new energy automobiles, rail transit and ships.

The invention provides a flame-retardant polyimide foam material, and a preparation method and application thereof. The novel flame-retardant polyimide foam material contains microcapsule fly ash, and the fly ash is further wrapped by two capsule materials in a specific form to form the flame-retardant polyimide foam material with a specific structure. The polyimide foam material provided by the invention contains the fly ash microcapsules, the fly ash has good flame retardant property, the aluminum hydroxide capsule material on the surface is decomposed by heating, a large amount of latent heat of evaporation is absorbed, the temperature of a combustion system is reduced, the flame retardant effect is realized, a large amount of water vapor is generated, the smoke generation rate and the smoke generation amount of a high polymer during combustion are reduced, the flame retardant and smoke suppression effect is realized, and the aluminum hydroxide is used for coating the fly ash, so that the synergistic flame retardant effect is expected to be realized in an application system. The melamine-formaldehyde capsule material (also called melamine resin) on the surface is a resin which is fine and crosslinked, very hard and good in thermal stability, and has higher mechanical strength, good heat resistance, water resistance, flame resistance, excellent electrical property and self-extinguishing property. The flame retardant has high flame retardant efficiency, has good compatibility with high polymers, can perform decomposition reaction at high temperature, absorb a large amount of heat, release ammonia, influence the melting behavior of materials and accelerate the carbonization of the materials into coke, and has simple preparation process and low cost.

According to the flame-retardant polyimide foam material provided by the invention, the fly ash microcapsule and the polyimide foam are compounded, and the addition amount of the microcapsule fly ash is particularly controlled, so that the polyimide foam has more excellent flame-retardant property by utilizing the flame-retardant property of the fly ash and the synergistic flame-retardant effect of the capsule material while the mechanical property and the heat insulation property of the polyimide foam are not influenced; and the preparation process is simple and easy to control, and is favorable for realizing industrial scale production and application.

Experimental results show that the density of the flame-retardant polyimide foam material prepared by the invention is 9.7kg/m³The compression strength is 15.3kPa, the thermal conductivity coefficient is 0.041W/(m.K), the oxygen index is 45 percent, the comprehensive performance is excellent, and the flame retardant property is outstanding.

For further illustration of the present invention, the following will describe in detail a flame retardant polyimide foam material and its preparation method and application in conjunction with the following examples, but it should be understood that these examples are carried out on the premise of the technical solution of the present invention, and the detailed embodiments and specific procedures are given only for further illustration of the features and advantages of the present invention, not for limitation of the claims of the present invention, and the scope of protection of the present invention is not limited to the following examples.

Example 1

Putting fly ash, aluminum sulfate and water into a three-neck flask containing 1% sodium hexametaphosphate dispersant solution according to the ratio of 1:2:5, stirring and dispersing at the speed of 500r/min, and heating to 70 ℃. 10% Na is added dropwise₂CO₃Adjusting pH of the aqueous solution to 6.5, stirring for 3 hr under heat preservation, cooling, filtering, washing, and drying to obtain powder A.

Putting melamine and formaldehyde into a three-neck flask according to the molar ratio of 1:3, heating the three-neck flask to 70 ℃ in a water bath, and adding 10% Na₂CO₃The pH value of the solution is adjusted to 8, and after standing for 1h, the melamine is completely dissolved to obtain a transparent solution, namely a melamine-formaldehyde resin prepolymer solution.

2% of dispersant is added into a three-neck flask, powder A and water are added according to the proportion of 1:6, and the mixture is fully stirred at the speed of 800 r/min. Adding the melamine-formaldehyde resin prepolymer solution, stirring and dispersing in a water bath at 60 ℃, and cooling to room temperature. Adjusting pH to 5 with HAc, heating in water bath, slowly heating to 60 deg.C, stirring while maintaining the temperature, cooling, adding 10% Na₂CO₃The solution was adjusted to pH 8. Filtering, washing and drying to obtain the microencapsulated fly ash coated by the melamine-formaldehyde resin.

Mixing 24 parts of BTDA and 30 parts of DMSO according to a formula, heating, stirring, heating to 80 ℃, and reacting for 6 hours; mixing 5 parts of microcapsule fly ash, 1.2 parts of methanol, 2 parts of polyether modified silicone oil and 0.5 part of dibutyltin dilaurate, and uniformly stirring; and (3) uniformly mixing the two solutions, adding 40 parts of PM-400, stirring at 3000r/min for 12s, injecting into a mold, and foaming and molding at room temperature. Baking and curing for 4h at 240 ℃ to obtain the novel flame-retardant polyimide foam material.

Example 2

Putting fly ash, aluminum sulfate and water into a three-neck flask containing 1% sodium hexametaphosphate dispersant solution according to the ratio of 1:2:5, stirring and dispersing at the speed of 500r/min, and heating to 70 ℃. 10% Na is added dropwise₂CO₃Adjusting pH of the aqueous solution to 6.5, stirring for 3 hr under heat preservation, cooling, filtering, washing, and drying to obtain powder A.

Putting melamine and formaldehyde into a three-neck flask according to the molar ratio of 1:3, heating the three-neck flask to 70 ℃ in a water bath, and adding 10% Na₂CO₃The pH value of the solution is adjusted to 8, and after standing for 1h, the melamine is completely dissolved to obtain a transparent solution, namely a melamine-formaldehyde resin prepolymer solution.

2% of dispersant is added into a three-neck flask, powder A and water are added according to the proportion of 1:6, and the mixture is fully stirred at the speed of 800 r/min. Adding the melamine-formaldehyde resin prepolymer solution, stirring and dispersing in a water bath at 60 ℃, and cooling to room temperature. Adjusting pH to 5 with HAc, heating in water bath, slowly heating to 60 deg.C, stirring while maintaining the temperature, cooling, adding 10% Na₂CO₃The solution was adjusted to pH 8. Filtering, washing and drying to obtain the microencapsulated fly ash coated by the melamine-formaldehyde resin.

Mixing 24 parts of BTDA and 30 parts of DMSO according to a formula, heating, stirring, heating to 80 ℃, and reacting for 6 hours; mixing 10 parts of microcapsule fly ash, 1.2 parts of methanol, 2 parts of polyether modified silicone oil and 0.5 part of dibutyltin dilaurate, and uniformly stirring; and (3) uniformly mixing the two solutions, adding 40 parts of PM-400, stirring at 3000r/min for 12s, injecting into a mold, and foaming and molding at room temperature. Baking and curing for 4h at 240 ℃ to obtain the novel flame-retardant polyimide foam material.

Example 3

Putting fly ash, aluminum sulfate and water into a three-neck flask containing 1% sodium hexametaphosphate dispersant solution according to the ratio of 1:2:5, stirring and dispersing at the speed of 500r/min, and heating to 70 ℃. 10% Na is added dropwise₂CO₃Adjusting pH of the aqueous solution to 6.5, stirring for 3 hr under heat preservation, cooling, filtering, washing, and drying to obtain powder A.

Putting melamine and formaldehyde into a three-neck flask according to the molar ratio of 1:3, heating the three-neck flask to 70 ℃ in a water bath, and adding 10% Na₂CO₃The pH value of the solution is adjusted to 8, and after standing for 1h, the melamine is completely dissolved to obtain a transparent solution, namely a melamine-formaldehyde resin prepolymer solution.

2% of dispersant is added into a three-neck flask, powder A and water are added according to the proportion of 1:6, and the mixture is fully stirred at the speed of 800 r/min. Adding the melamine-formaldehyde resin prepolymer solution, stirring and dispersing in a water bath at 60 ℃, and cooling to room temperature. Adjusting pH to 5 with HAc, heating in water bath, slowly heating to 60 deg.C, stirring while maintaining the temperature, cooling, adding 10% Na₂CO₃The solution was adjusted to pH 8. Filtering, washing and drying to obtain the microencapsulated fly ash coated by the melamine-formaldehyde resin.

Mixing 24 parts of BTDA and 30 parts of DMSO according to a formula, heating, stirring, heating to 80 ℃, and reacting for 6 hours; mixing 15 parts of microcapsule fly ash, 1.2 parts of methanol, 2 parts of polyether modified silicone oil and 0.5 part of dibutyltin dilaurate, and uniformly stirring; and (3) uniformly mixing the two solutions, adding 40 parts of PM-400, stirring at 3000r/min for 12s, injecting into a mold, and foaming and molding at room temperature. Baking and curing for 4h at 240 ℃ to obtain the novel flame-retardant polyimide foam material.

Comparative example

Mixing 24 parts of BTDA and 30 parts of DMSO according to a formula, heating, stirring, heating to 80 ℃, and reacting for 6 hours; mixing 1.2 parts of methanol, 2 parts of polyether modified silicone oil and 0.5 part of dibutyltin dilaurate, and uniformly stirring; and (3) uniformly mixing the two solutions, adding 40 parts of PM-400, stirring at 3000r/min for 12s, injecting into a mold, and foaming and molding at room temperature. And baking and curing for 4 hours at 240 ℃ to obtain the polyimide foam material.

The novel flame-retardant polyimide foam material prepared in the embodiment of the invention and the polyimide foam material prepared in the comparative example are subjected to performance detection.

The density test standard is GB/T6343-.

Referring to table 1, table 1 shows the performance test results of the novel flame retardant polyimide foam prepared in the inventive example and the polyimide foam prepared in the comparative example.

TABLE 1

As can be seen from the data in Table 1, after the microcapsule fly ash is added to the polyimide foam material, the compression performance and the heat conductivity coefficient are slightly affected, the flame retardant performance is obviously improved, after 15 parts of microcapsule fly ash are added, the oxygen index reaches 45%, and compared with the polyimide foam material without the microcapsule fly ash, the flame retardant effect is obvious.

While the present invention has been described in detail with respect to a flame retardant polyimide foam material and methods of making and using the same, the principles and embodiments of the present invention are described herein using specific examples, which are set forth only to facilitate an understanding of the methods and their core concepts, including the best mode, and to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention. The scope of the invention is defined by the claims and may include other embodiments that occur to those skilled in the art. Such other embodiments are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.